U.S. patent number 5,011,297 [Application Number 07/587,032] was granted by the patent office on 1991-04-30 for apparatus for detecting the temperature of an object on a coordinate measuring apparatus.
This patent grant is currently assigned to Carl-Zeiss-Stiftung. Invention is credited to Jakob Tittl.
United States Patent |
5,011,297 |
Tittl |
April 30, 1991 |
**Please see images for:
( Certificate of Correction ) ** |
Apparatus for detecting the temperature of an object on a
coordinate measuring apparatus
Abstract
An apparatus for detecting temperature of an object to be
measured such as a workpiece mounted on a coordinate measuring
apparatus having a movable measuring arm. The measuring apparatus
includes a sensing pin or complete sensing head as well as a
temperature sensor. For measuring temperature, the sensing pin or
sensing head is exchange for the temperature sensor having the same
kind of holder as the sensing pin. Thereafter, the temperature
sensor is moved to the object by the measuring arm of the apparatus
and is placed in contact therewith. The registered temperature
measurement values are used to correct the lengths and spacings
measured with the coordinate measuring apparatus. The entire
temperature and coordinate measuring operation is carried out
completely automatically by the CNC control of the apparatus
without the aid of operating personnel. A temperature sensor for
carrying out the method of the invention is also disclosed.
Inventors: |
Tittl; Jakob (Sontheim/Brenz,
DE) |
Assignee: |
Carl-Zeiss-Stiftung
(Heidenheim, DE)
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Family
ID: |
6358374 |
Appl.
No.: |
07/587,032 |
Filed: |
September 24, 1990 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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369517 |
Jun 21, 1989 |
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Foreign Application Priority Data
Current U.S.
Class: |
374/141; 33/560;
33/702; 33/DIG.19; 374/142; 374/E1.018 |
Current CPC
Class: |
G01B
5/0014 (20130101); G01K 1/14 (20130101); Y10S
33/19 (20130101) |
Current International
Class: |
G01B
5/00 (20060101); G01K 1/14 (20060101); G01K
001/14 (); G01K 013/00 (); G01D 003/04 () |
Field of
Search: |
;33/503,504,556,557,558,559,560,561,702,704,DIG.19
;374/141,142 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1015614 |
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Sep 1957 |
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DE |
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3013378 |
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Oct 1981 |
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DE |
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3620118 |
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Dec 1987 |
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DE |
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3729644 |
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Mar 1989 |
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DE |
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0103367 |
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Aug 1979 |
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JP |
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Other References
Product Publication 60-20-027-d entitled
"Tasterwechseleinrichtungen" of Carl Zeiss (1986). .
International patent application PCT/GB 86/00551 (WO87/01798), Mar.
1987..
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Primary Examiner: Cuchlinski, Jr.; William A.
Assistant Examiner: Gutierrez; Diego F. F.
Attorney, Agent or Firm: Ottesen; Walter
Parent Case Text
This is a division of application Ser. No. 369,517, filed June 21,
1989.
Claims
What is claimed is:
1. In a coordinate measuring apparatus having a movable measuring
arm for moving and releasably engaging a plurality of coordinate
measuring sensor components, each of the coordinate measuring
sensor components having a holder which enables the coordinate
measuring sensor components to be exchanged one for the other, a
temperature sensor component for measuring the temperature of an
object being measured by said coordinate measuring apparatus, the
temperature sensor component comprising:
a temperature sensor holder having a form corresponding to the form
of the holder of each of said coordinate measuring sensor
components, whereby said temperature sensor component is exchanged
with one of said coordinate measuring sensor components to measure
the temperature of the object.
2. The temperature sensor component of claim 1, the coordinate
measuring apparatus including a magazine disposed at the periphery
of the apparatus for holding the temperature sensor component and
the coordinate measuring sensor components.
3. The temperature sensor component of claim 1, comprising: a
temperature sensor for detecting temperature; and, pivot means for
pivotally connecting said temperature sensor to said temperature
sensor holder.
4. The temperature sensor component of claim 1, comprising: a
temperature sensor for detecting temperature; and, resilient means
for resiliently connecting said temperature sensor to said
temperature sensor holder.
5. The temperature sensor component of claim 1, comprising: a
temperature sensor for detecting temperature; contact means formed
in said temperature sensor holder; and, a connecting cable for
connecting said temperature sensor with said contact means.
6. The temperature sensor component of claim 1, the coordinate
measuring apparatus including an evaluation circuit; and, said
temperature sensor component further comprising: a temperature
sensor for detecting temperature; means for connecting said
temperature sensor to said temperature sensor holder; and, a
flexible cable connecting said temperature sensor directly to said
evaluation circuit.
7. The temperature sensor component of claim 1, comprising: a
temperature sensor for detecting temperature; means for connecting
said temperature sensor to said temperature sensor holder; and,
means for wirelessly transmitting the values of temperature
measured by said temperature sensor to said coordinate measuring
apparatus.
Description
BACKGROUND OF THE INVENTION
In coordinate measurement technology, the temperature of a
workpiece to be measured by the coordinate measuring apparatus must
be detected to approximately 0.1K for precise length measurements.
Known contactless operating temperature sensors have up to now not
been capable to detect temperatures with this precision. Therefore,
contact thermometers have been applied to the object to be measured
by operating personnel for detecting temperature. Precision
resistors are used which are connected to an evaluation circuit of
the coordinate measuring apparatus. The measurement values of these
precision resistors are used together with the measurement values
of further contact thermometers permanently installed on the scales
of coordinate measuring apparatus for correcting the length
measurement values of the workpiece to the dimensions applicable
for a reference temperature of 20.degree. C. Such a method is
disclosed for example in published German patent application DE 36
20 118 A1.
The known method of temperature detection therefore requires the
presence of an operating person who applies the contact thermometer
to the workpiece or object. Coordinate measuring apparatus are now
increasingly used in production measurement operation in order to
measure a larger number of workpieces fed continuously via a
handling system or mounted on a measuring table. This production
measuring operation can for example be a computerized numerical
control (CNC) in a night shift without personnel in attendance. The
temperature compensation of the coordinate measuring values cannot
take place continuously during the shift since the temperature is
measured only once in advance of the shift. A change in the
temperature of the workpiece to be measured during the shift leads
inexorably to a measurement error.
Published German patent application DE 36 20 118 A1 also discloses
that the temperature detection can be automated for workpieces
which are to be measured within a flexible manufacturing system.
This automatization is achieved by installing a reference body
(gauge block) on the pallet of the workpiece. This gauge block
passes through the manufacturing process together with the
workpiece and therefore takes on the same temperature. The
coordinate measuring apparatus then detects the temperature of the
workpiece to be measured via a length measurement on this reference
body.
Although this method of temperature detection is suitable for
workpieces in the manufacturing area, it does however present
disadvantages in the series measurement operation. Error influences
caused by temperature gradients in the measurement region of the
coordinate measuring apparatus or within the workpiece itself
cannot be detected because the temperature at the workpiece itself
is not directly measured in a series measurement operation.
A method is disclosed in German Patent 3,013,378 wherein workpieces
are automatically fed to a measuring arrangement provided with a
temperature sensor and are measured with respect to their spatial
dimensions and their temperature. The known method is however
poorly suited when workpieces having different geometries are to be
automatically measured. A complex handling system is then required
in order to bring the temperature sensor in contact with the
workpiece.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a method for detecting
the temperature of objects to be measured on a coordinate measuring
apparatus which permits an automatic operation without attending
personnel and to provide a reliable and precise detection of
measured values with the least amount of effort.
The method of the invention is for detecting the temperature of an
object or workpiece to be measured on a coordinate measuring
apparatus. The apparatus has a computer, a movable measuring arm
and a magazine for holding components of the apparatus with the
magazine being disposed at the periphery of the apparatus. The
method includes the steps of: moving the measuring arm with a
coordinate measuring sensor component releasably engaged therewith
to the magazine; dropping the coordinate measuring sensor component
off in the magazine and exchanging the same for a temperature
sensor component so that the latter is now releasably engaged with
the measuring arm; moving the temperature sensor component
releasably engaged with the measuring arm into contact with the
object and maintaining the contact for a predetermined time
duration; transmitting the measured values of temperature detected
by the temperature sensor component to the computer of the
coordinate measuring apparatus; and then, moving the temperature
sensor component with the measuring arm back to the magazine and
exchanging the same for the coordinate measuring sensor
component.
According to a feature of the invention, the sensor for detecting
the workpiece temperature is brought into contact with the
workpiece neither by an attending person nor by a complex
additional handling system; instead, the sensor is brought into
contact with the workpiece by the measuring arm of the coordinate
measuring apparatus itself. This takes place in that the sensing
pin usually used for the coordinate measurements or the entire
sensing head is exchanged for a temperature sensor. On the one hand
then, the method presupposes the use of a coordinate measuring
apparatus which has an automatic sensing pin exchange unit and
requires, on the other hand, that the temperature sensor held in
operational readiness in lieu of the sensing pin is provided with a
holder which corresponds in its form to the holder of the
exchangeable coordinate measuring sensing pin.
Coordinate measuring apparatus with automatic sensing pin exchange
units are known per se and are described, for example, in the
product information bulletin number 60-20-027-d published in 1986
under the title "Tasterwechseleinrichtungen" by Carl Zeiss, an
organization doing business in the Federal Republic of Germany.
Such apparatus are also disclosed in European Patent publication 01
28 464 as well as in U.S. Pat. No. 4,637,119 corresponding thereto.
Such exchange units include a magazine disposed in the measuring
region of the coordinate measuring apparatus wherein the different
exchangeable sensing elements are stored. The additional effort
needed for an automatic temperature measurement with such a system
then simply involves hanging a temperature sensor with an
appropriate mounting into this magazine and to integrate the
corresponding exchange operations and sensing operations with the
temperature sensor into the control program for the coordinate
measuring apparatus.
The sensor with its contact surface is resiliently attached to the
holder by means of which it is connected to the coordinate
measuring apparatus so that a reliable contact can be made with the
temperature sensor on the workpiece surface inclined with respect
to the machine axes. In addition, it is advantageous to attach the
sensor to the holder so that it is rotatable or pivotable. The
sensor can then be aligned in advance with respect to the side of
the workpiece to be contacted.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described with reference to the drawings
wherein:
FIG. 1 is a perspective schematic of a portion of the magazine in
which the coordinate measuring sensor and a temperature sensor are
held in operational readiness;
FIG. 2 is a schematic side elevation view of the temperature sensor
shown in FIG. 1;
FIG. 3a is a side elevation view of another embodiment of a
temperature sensor slightly modified when compared to the
temperature sensor of FIG. 2;
FIG. 3b is a plan view of the holder of the temperature sensor of
FIG. 3a; and,
FIG. 4 is a perspective view of a complete coordinate measuring
apparatus in which a temperature sensor according to a third
embodiment of the invention has been exchanged.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
The magazine shown in FIG. 1 corresponds in its configuration to
the magazine of the sensor exchange unit described in U.S. Pat. No.
4,637,119 incorporated herein by reference. The magazine is
described in detail in this patent and the following description
makes reference thereto.
An exchangeable sensor pin combination 21 is hooked into one of the
two magazine positions which in FIG. 1 is position 47. The sensing
pin combination 21 includes a holder 16 in the form of a rotatable
part 16 in which a three-point bearing is fitted. The three-point
bearing is comprised of the three pairs of balls 15a by means of
which the sensing-pin combination 21 engages the corresponding
bearing support in the sensing head of the coordinate measuring
apparatus. A steel plate 18 fitted into the rotatable part 16 acts
as an armature for the electromagnetic holding device located in
the sensing head.
A temperature sensor 1 is hooked into the second magazine position
37. This temperature sensor 1 has the same holder 6 as the
sensing-pin combination 21. The holder 6 includes corresponding
bearing balls 5a and a corresponding steel plate 8.
As shown in the side elevation view of FIG. 2, the actual measuring
component 10 of the temperature sensor is embedded in a contact
plate 15.
This contact plate assures the heat transfer from the workpiece to
the sensor itself and therefore has a good heat conductivity and a
low heat capacity. A thin copper disc can, for example, be used for
this purpose. The copper disc is silver coated on the outside to
keep out temperature radiation from the vicinity of the measuring
component. The copper disc is attached to a first holding plate 4
via an insulating intermediate layer. The actual measuring
component 10 itself can, for example, be a temperature sensor PT
100 (platinum resistor) as sold for example under the designation
GR 2102 by the Degussa Company of Frankfurt, Federal Republic of
Germany.
The first holding plate 4 is connected to a second holding plate 3
with the aid of four springs (9a, 9b). This resilient connection
assures that the contact plate 15 can be set down on surfaces of
the workpiece to be measured which are not precisely axially
parallel.
The second holding plate 3 is, in turn, connected via a joint 2 so
as to be rotatable about an axis 14 and is attached to the holder 6
so as to be pivotable about pin 13. In this way, the contact plate
15 can be coarsely prealigned with reference to the geometry of the
workpieces to be measured.
The connecting cable 12 of the measuring component 10 is coiled
many times about a wire 11 attached to the holder 6 in order to
relieve tension loading. The cable 12 is connected with an
appropriate electronic circuit for measuring temperature at the
coordinate measuring apparatus.
The embodiment shown schematically in FIGS. 3a and 3b can also be
used for transmitting the signals of the measuring component
10.
In the embodiment shown in FIGS. 3a and 3b, a plurality of contact
pins 114 are provided at the peripheral edge of the exchanging
surface of the holder 106. The connecting cables 112 of the
measuring component 110 are, for example, connected to the contact
pins 114. These pins conduct the measurement signals to
corresponding countercontacts at the receiver on the measuring arm
of the coordinate measuring apparatus. The embodiment described
with reference to FIGS. 3a and 3b is suitable especially for the
case wherein the coordinate measuring apparatus is not equipped
with an exchanging unit for the sensing pins and is instead
equipped with an exchanging unit for complete sensing heads which
anyhow require connectors for supply voltages and for transmitting
the sensing signal further and the like.
In addition to the possibilities illustrated here of the direct
transmission of the measurement signal of the temperature sensor
via cables, it is also possible to provide for a wireless
transmission of the signal of the measurement component to the
coordinate measuring apparatus. In this case, the temperature
sensor has its own voltage supply in the form of a battery as well
as a suitable transmitter for transmitting the measured value.
The operation of detecting temperature with such a temperature
sensor will be described below with respect to FIG. 4.
The coordinate measuring apparatus 200 shown in FIG. 4 has a
magazine 208 within its measuring region. In this magazine 208,
several exchangeable sensing pins as well as a temperature sensor
201 are held in operational readiness. When a temperature
measurement is to be made on one of the four workpieces (204, 205,
206 or 207) secured to the table, the measuring arm 209 travels to
the magazine 208 and places the sensing pin which was needed in the
previous coordinate measuring program, into one of the vacant
magazine positions. Thereafter, the temperature sensor 201 is taken
out of the magazine 208 in the course of the automatic exchange
operation and, in lieu of the sensing pin just set down, the
temperature sensor is tightly engaged in the sensing head 211 which
is attached to the lower end of the measuring arm 209.
The measuring arm moves in correspondence to the programmed
measuring operation with the temperature sensor 201 to the
workpiece whose temperature is to be measured. Here, the measuring
arm applies the even contact plate having the temperature measuring
element to one of the even surfaces of the workpiece. The contact
plate is located at the lower end of the sensor 201. This case is
illustrated in FIG. 4.
The contact between the measuring element and the workpiece must be
maintained for a period of time so that the measuring element can
take on the temperature of the workpiece. This time period is
dependent upon the response time of the measuring element or of the
heat capacity of the contact plate on the lower side of the sensor
and can be predetermined by means of experimentation. With the
configuration of the sensor shown in FIG. 2, contact times of less
than six seconds and a measurement precision for a temperature of
5.degree./100.degree. C. can be obtained.
The temperature measurement values are then transmitted wirelessly
to a corresponding remote station 203 by a unit (not shown) on the
temperature sensor 201. The remote station 203 is connected with
the control 202 of the coordinate measuring apparatus. In this
connection, it should be mentioned that it is advantageous to
detect and store the measured values of temperature during the
entire contact operation. The different measured values can then be
subjected to a plausibility check which permits a statement to be
made that the sensor was actually in contact with the workpiece.
This can be recognized in that the temperature converges from a
previously constant value corresponding to air temperature to a
somewhat different temperature value of the workpiece during the
contact.
After the temperature detection is completed, the measuring arm 209
again moves to the magazine 208 and there exchanges the temperature
sensor 201 and takes up the appropriate sensing pin required for
the actual coordinate measuring program.
All coordinate measurements on the workpiece 204 which are
thereafter carried out with the aid of the sensing pin are then so
corrected with the aid of a corresponding computer program that
they correspond to the dimensions of the workpiece at the reference
temperature of 20.degree. C.
It is understood that the foregoing description is that of the
preferred embodiments of the invention and that various changes and
modifications may be made thereto without departing from the spirit
and scope of the invention as defined in the appended claims.
* * * * *